KEYWORDS: LCDs, Systems modeling, Monte Carlo methods, Light sources and illumination, Chromium, Reflectors, Light, Ray tracing, Liquid crystals, Performance modeling
Transflective LCDs use both reflective and transmissive elements in order to remain readable under
strong ambient light conditions through light recycling. A transflective LCD illumination system based
on the dual cell gap structure is simulated and compared to a regular LCD to assess contrast
performance under influence of ambient light in terms of a user viewable image. Previous studies in
the literature have not developed full system model simulations that include image output, glare and
light leakage due to both microstructure geometry and polarization. The overall contrast performance
is evaluated for a wide range of ambient source strengths using three different contrast metrics (ANSI,
NIST and a proposed illuminance distribution contrast method). Three ambient source types (planar
Lambertian, planar isotropic and a parabolic reflector) are used to simulate both office and outdoor
environments. The sources were selected to simulate both specular and diffuse components of ambient
lighting. The proposed contrast performance relationship between the different components of
polarization leakage, microstructure leakage, and glare for both ambient and nominal backlight sources
was verified in the Monte Carlo simulation models. The proposed contrast performance relationship
provides a new understanding into the proper design of transflective LCD devices as control of the
dark feature or black level illuminance is highly important. The proposed distribution contrast method
proved to be more accurate and sensitive in assessing contrast performance than the NIST and ANSI
methods. The transflective system was able to attain an average contrast performance of 10X beyond
that of the regular LCD.
This past spring a new for-credit course on illumination engineering was offered at the College of Optical Sciences at
The University of Arizona. This course was project based such that the students could take a concept to conclusion. The
main goal of the course was to learn how to use optical design and analysis software while applying principles of optics
to the design of their optical systems. Projects included source modeling, displays, daylighting, light pollution, faceted
reflectors, and stray light analysis. In conjunction with the course was a weekly lecture that provided information about
various aspects of the field of illumination, including units, étendue, optimization, solid-state lighting, tolerancing, litappearance
modeling, and fabrication of optics. These lectures harped on the important points of conservation of
étendue, source modeling and tolerancing, and that no optic can be made perfectly. Based on student reviews, future
versions of this course will include more hands-on demos of illumination components and assignments.
The optical vortex coronagraph is a promising scheme for achieving high contrast low loss imaging
of exoplanets as close as 2λ/D from the parent star. We describe results using a high precision
vortex lens that was fabricated using electron-beam lithography. We also report demonstrations of
the coronagraph on a telescope employing a tip-tilt corrector.
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